Methane

Massive amounts of methane venting from the seabed, penetrating the sea ice, and entering the atmosphere over the Arctic Ocean. Faultlines indicate a further danger, i.e that earthquakes could trigger clathrate destabilization.

Sam Carana in 2014: "The amounts of methane being released from hydrates will be greater than the methane that actually reaches the atmosphere. To put a figure on the latter, my estimate is that emissions from hydrates and permafrost currently amount to 100 Tg annually, a figure that is growing rapidly. This 100 Tg includes 1 Tg for permafrost, similar to IPCC estimates."

Sediments underneath the Arctic Ocean hold vast amounts of methane. Just one part of the Arctic Ocean alone, the East Siberian Arctic Shelf (ESAS, rectangle on map below), holds up to 1700 Gt of methane. A sudden release of just 3% of this amount could add over 50 Gt of methane to the atmosphere, and experts consider such an amount to be ready for release at any time (see above image).

Total methane burden in the atmosphere now is 5 Gt. The 3 Gt that has been added since the 1750s accounts for almost half of the (net) total global warming caused by people. The amount of carbon stored in hydrates globally was in 1992 estimated to be 10,000 Gt (USGS), while a more recent estimate gives a figure of 63,400 Gt (Klauda & Sandler, 2005). The ESAS alone holds up to 1700 Gt of methane in the form of methane hydrates and free gas contained in sediments, of which 50 Gt is ready for abrupt release at any time.

Imagine what kind of devastation an extra 50 Gt of methane could cause. Imagine the warming that will take place if the methane in the atmosphere was suddenly multiplied by 11. Whiteman et al. recently calculated that such an event would cause $60 trillion in damage. By comparison, the size of the world economy in 2012 was about $70 trillion.

For the past 420,000 years, temperatures typically moved up and down by roughly 10°C or 18°F between a glacial and interglacial phase of the ice ages, suggesting that a 100 ppm rise of carbon dioxide and 300 ppb rise of methane go hand in hand with a 10°C temperature rise. By implication, current levels of carbon dioxide in the atmosphere appear to have us locked in for a future temperature rise of more 10°C. For methane, the equation looks at least three times as bad.

While carbon dioxide emissions get a lot of attention (and they definitely must be cut rapidly and dramatically), the rise of methane is possibly even more worrying. The image below shows the historic rise (1750-2015) of methane (CH4), carbon dioxide (CO₂) and nitrous oxide (N2O).

Historic rise of methane, carbon dioxide and nitrous oxide

According to NOAA data, annual mean global methane grew from 2004-2013 by an average of 3.75 ppb per year. In 2014, the growth rate was 12.56 ppb. In 2015, the growth rate was 10.14 ppb. According to the WMO, methane's 2014–2015 absolute increase was 11 ppb.
(Also see above image #16: Methane's Rise since 2000)

IPCC AR5 (2013) figures for methane's lifetime and methane's Global Warming Potential (GWP) over 20 and 100 years are in the top right-hand panel below. In the panel underneath is the formula used to calculate GWP.

Note that Shindell et al. pointed out in 2009 that when including some important direct and indirect effects, methane's GWP is 105 over 20 years (see image below). Over shorter periods, the GWP is even higher, as illustrated by above image below. Over a 10-year timescale, methane's GWP is 130, as calculated by Sam Carana based on Shindell's data. Over a 10-year timescale, the current global release of methane from all anthropogenic sources exceeds all anthropogenic carbon dioxide emissions as agents of global warming; that is, methane emissions are more important than carbon dioxide emissions for driving the current rate of global warming, as illustrated by the graph in the left-hand panel of above image. Unlike carbon dioxide, methane's GWP does rise as more of it is released.

In the context of tipping points, which is most appropriate regarding methane releases in the Arctic, it makes sense to focus on a short time horizon, i.e. as short as a few years, rather than decades. Sam Carana calculates that, based on figures by Shindell et al., methane's GWP is more than 130 times that of carbon dioxide over a period of 10 years.

A 2009 study by Drew Shindell et al. points out that IPCC figures do not include direct+indirect radiative effects of aerosol responses to methane releases that increase methane's GWP to 105 over 20 years when included.

In the context of tipping points, which is most appropriate regarding methane releases in the Arctic, it makes sense to focus on a short time horizon, i.e. as short as a few years, rather than decades.

As image 7.b (left) shows, based on the figures by Shindell et al. and using a horizon of 10 years, methane's GWP is more than 130 times that of carbon dioxide.

In image 7.b, the blue line is based on IPCC AR4 figures. The red line is based on figures from the study by Shindell et al., which also concludes that methane's GWP would likely be further increased when including ecosystem responses.

Even more important than methane's high immediate GWP is methane's local warming potential (LWP), which includes the indirect effect of triggering further releases. In case of a large abrupt release, methane's lifetime will be extended, due to hydroxyl depletion. Much of the methane can be expected to persist locally for decades, at its highest LWP, since there's very little hydroxyl in the atmosphere above the Arctic in the first place, so very little methane will get oxidized there. The impact of such an abrupt release will be felt most strongly in the Arctic, where the release took place. Since it will take time for methane to spread away from the Arctic, much of the entire release will remain concentrated above the Arctic.

The additional warming that this will cause in the Arctic will make the sea ice decline even more dramatically than is already the case now. The combined LWP of snow cover loss, sea ice loss and methane releases in the Arctic is huge. This is bound to trigger further releases of methane in the Arctic, and their joint impact will accumulate, as illustrated in the next image.

Smaller releases of methane in the Arctic come at great risk; their explosive eruption from the seafloor and their huge local warming impact threatens to further destabilize sediments under the Arctic Ocean and trigger further methane releases.

With continued warming of the Arctic Ocean, heat increasingly threatens to reach the seafloor of the Arctic Ocean and unleash huge methane eruptions from destabilizing clathrates. The threat is that runaway warming will strike first in the Arctic, to spread from there, causing heatwaves and firestorms across North America and Siberia, while adding massive amounts more soot and carbon dioxide to the atmosphere globally, as forests, peat bogs and tundras at higher latitudes burn, with the threat of escalating into runaway global warming, causing huge temperature swings and extreme weather events, and contributing to increasing depletion of fresh water and food supply.

This image shows the rise of methane levels from 1984, created with World Metereological Organization (WMO) data up to 2014. The square marks a high mean 2015 level, from NOAA's MetOp-2 satellite images, and it is added for comparison, so it does not influence the trendline, yet it does illustrate the direction of rise of methane levels and the threat that global mean methane levels will double well before the year 2040.

Growth in methane levels has been accelerating recently. Contained in existing data is a trend indicating that methane levels could increase by a third by 2030 and could almost double by 2040. Unlike carbon dioxide, methane's GWP does rise as more of it is released. Methane's lifetime can be extended to decades, in particular due to depletion of hydroxyl in the atmosphere.

The image below compares mean methane levels on the morning of April 22 between the years 2013 to 2017, confirming that methane levels are rising most strongly at higher altitudes, say between 6 to 17 km (which is where the Troposphere ends at the Equator), as compared to altitudes closer to sea level. This strong rise at higher altitudes may not be as noticeable when taking samples from ground stations. This was discussed in earlier posts such as in this post, in this post and in this post.

The danger is that, as Arctic sea ice continues to decline, more heat will reach the seafloor and will destabilize methane hydrates contained in sediments at the bottom of the Arctic Ocean, resulting in huge methane eruptions.

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The Climate Plan calls for comprehensive action through multiple lines of action implemented across the world and in parallel, through effective policies such as local feebates. The Climate Plan calls for a global commitment to act, combined with implementation that is preferably local. In other words, while the Climate Plan calls for a global commitment to take comprehensive and effective action to reduce the danger of catastrophic climate change, and while it recommends specific policies and approaches how best to achieve this, it invites local communities to decide what each works best for them, provided they do indeed make the progress necessary to reach agreed targets. This makes that the Climate Plan optimizes flexibility for local communities and optimizes local job and investment opportunities.

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Global temperatures are rising fast. In the Arctic, temperatures are rising even faster (interactive charts below and right). For 2010 and 2011, NASA recorded anomalies of over 2°C at higher latitudes (64N to 90N), with anomalies of over 3°C at latitudes 79N and 81N in 2010.

For November 2010, anomalies of 12.5°C were recorded at latitude 71N, longitude -79 (Baffin Island, Canada). At specific moments in time and at specific locations, anomalies can be even more striking. As an example, on January 6, 2011, temperature in Coral Harbour, located at the northwest corner of Hudson Bay in the province of Nunavut, Canada, was 30°C (54°F) above average.